Piston



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HARRY F WOOD BY @mi HIJ H. F. WOOD PISTON Filed March '7, 1942 Feb. 15, 1944. H. F. wooD 2,341,836

PISTON Filed-March '7, 1942 2 Sheets-Sheet 2 224 276 asa (227 `244s as? INVENTOR. HARRY E WOOD 111 ATTORNEY Patented F eb. 15, 1944 UNITED STATES PATENT OFFICE PISTON Application March 7, 1942, Serial No. 433,763

18 Claims.

This invention relates to pistons and has particular reference to pistons for an internal combustion engine.

It is an object of this invention to provide a piston which may be formed almost entirely from stamped sheet metal parts at less expense than an aluminum or centrifugally cast steel piston of similar size.

It is another object of this invention to provide a piston which will be relatively light and which will have a relatively low coefficient of expansion.

It is another object of this invention to provide a piston which combines high heat conducting capacity with a low rate of expansion approximately equal to the rate of expansion of a cast iron cylinder in which it is arranged to operate.

1t is another object of this invention to provide novel means for bracing a stamped piston, which brace means will increase the ability of the piston to conduct heat away from its face.

It is another object of this invention to provide novel bracing means for a stamped piston which will adequately brace the walls rof the piston while maintaining the weight of the piston at a minimum.

It is another object of this invention to provide a piston with thinner wall thickness to increase the rate of heat transfer through the piston.

It is another object of this invention to provide a piston formed of stampings joined together in such a Way as to form a series of I-sections throughout the face of the piston.

Other objects and advantages of this invention will be apparent from a consideration of the following description and claims and the attached drawings, of which there are two sheets, and in which- Figure 1 represents a plan view of the preferred form of the piston;

Figure 2 represents an elevational View of the preferred form of the piston in operative position in a cylinder (shown in cross section) Figure 3 represents a sectional view taken along a plane indicated by the line 3-3 in Figure 2 and looking in the direction of the arrows;

Figure 4 represents a vertical sectional view taken along a plane indicated by the line 1 -Il in Figure 2 and looking in the direction of the arrows;

Figure 5 represents a vertical sectional view taken along a plane indicated by the line 5-5 in Figure 1 and looking in the direction of the arrows;

Figure 6 represents a plan view of the inner reinforcing member shown in Figures l through 5;

Figure 7 represents a vertical sectional view through a modified form of the piston;

Figure 8 represents a sectional View taken along a plane indicated by the line 8--8 in Figure 7 and looking in the direction ofthe arrows;

Figure 9 represents a partial horizontal sectional view taken along a plane indicated by the line 9-9 in Figure 7 and looking in the direction of the arrows;

Figure 10 represents a vertical sectional view through a further modified form of the piston;

Figure 11 represents a vertical sectional view taken along a plane indicated by the line I I-II in Figure 10 and looking in the direction of the arrows; and

Figure 12 represents a partial horizontal sectional view taken along a plane indicated by the line I2-l2 in Figure l0 and looking in the direction of the arrows. In the past it has been the practice to make pistons for internal combustion engines from either cast iron or cast aluminum material. Cast iron has the disadvantage of being relatively heavy and of relatively poor heat conductivity while aluminum has the disadvantage of a relatively high coefcient of expansion which is higher than the coeicient of expansion of the usual cast iron cylinder block in which the piston operates. This requires that provision be made in the piston for accommodating expansion of the piston. Both aluminum and cast iron pistons require a considerable number of machining operations which increase the final cost of the pistons.

This invention provides a piston which is formed of several stampings which may conveniently be formed from light gauge sheet steel. The size of the stampings may be very closely regulated so that very few machining operations are required to finish the piston. The various stampings may be inexpensively formed and secured together by a hydrogen welding process which will be more particularly described later. The sheet steel has a lower coefficient of eXpansion than aluminum and a higher rate of heat conductivity than cast iron so as to avoid the disadvantages of each of these metals. 'I'he steel will expand at about the same rate as the cylinder in which it operates so that the skirt of the piston need not be split.

In the preferred form of the invention illustrated in Figures 1 through 6, there is-disclosed, by way Qi example, a piston 20 consisting of an outer cylindrical member 22 which has an upper portion 24 of reduceddiameter joined with the main cylindrical portion 22 by the annular shoulder 26. The upper face 28 of the upper cylindrical portion 24 is slightly domed and defines an aperture 38 in the center of the piston for a purpose which will be described presently. Opposite walls of the main cylindrical portion 22 are pressed inwardly as at 32 and extruded inwardly at 34 along a diameter of the cylinder. A flange 35 is turned inwardly and upwardly around the lower end of th'e cylindrical member 22 to stiffen the lower end of the piston. The ilange 35 forms an annular groove from which oil that may collect therein is permitted to drain through holes 31 onto the cylinder wall 63.

An inner cylindrical member 36 having an outside diameter approximately equal to the inside diameter of the reduced cylindrical portion 24 of the outer cylindrical member is tightly pressed within the reduced cylindrical portion and extends downwardly therebelow in spaced relationship with the main portion of the cylindrical member 22. Opposite the inwardly pressed portions 32 of the outer cylindrical member, the inner cylindrical member 36 is also provided with inwardly pressed portions 38 which are also extruded as at 40 along the same diameter as the extrusions 34 in the outer cylindrical member. The extruded portions 34 and 40 on each side of the piston serve to support the longitudinally spaced, co-axialbearing sleeves 42 Within which the wrist pin 44 is received. Snap rings 46 are positioned within each end of the bearing sleeves 42 to retain the wrist pin in position.

The upper wall 48 of the inner cylindrical member 36 is pressed upwardly in a series of circular domes U which are arranged to bear against the underside of the top wall 28 of the outer cylindrical member 22. The domes 50 serve to support the top wall 28 from the inner cylindrical member 36 and to assist in conducting heat away from the face of the piston. The upper wall 48 of the inner member also defines an elongated aperture 52 generally oval shaped having its major axis extending transversely across the axis of the wrist pin 44. A flange 54 is extruded upwardly around the edge of the aperture 52.

Immediately over the ends of the wrist pin 44, the side walls of the inner cylindrical member 36 are pressed radially inwardly to form ribs 56 which extend vertically between the inwardly pressed portions 38 and the top wall 48 of the inner cylindrical member. The ribs thus formed serve to reinforce the inner cylindrical member and transmit loads between the face of the piston and the wrist pin 44. The side walls of the'inner cylindrical member 36 are cut away symmetrically with respect to a diameter of the piston perpendicular to the wrist pin 44 as at 58. This reduces the weight of the piston without weakening the bracing effect of the inner cylindrical member on the piston as a whole.

y Positioned around the upper portion 24 of the outer cylindrical member 22 and resting upon the annular shoulder 26 is a cylindrical sleeve 60 which is conveniently formed of cast iron or other suitable material. The sleeve 66 is provided with three annular grooves 62 within which are positioned the usual compression rings 64 and an oil ring 66. The oil ring 66 is provided with the usual external and internal grooves connected by oil holes 68 through which oil wiped from the cylinder walls may pass through the oil ring to the grooves 62 in which it is positioned. Holes In are formed in the upper portion 24 of the outer cylindrical member, the inner cylindrical member 36 and the sleeve 60, communicating with the oil ring groove 62 and conduct the oil wiped'o the cylinder walls 63 back to the engine through the center of the piston and cylinder in which the piston operates.

The ring retaining sleeve 60 is retained in place on the shoulder 26 by a cap member 12 which is slightly dome shaped so as to fit on top of the dome shaped upper wall 28 of the outer cylindrical member 22. A downturned annular flange 'I4 along the rim of the cap member 12 is arranged to bear against the upper end of the ring retaining sleeve 60 while a downwardly pressed point 16 formed in the center of the cap member 12 is arranged to project through the aperture 30 in the upper wall 48 and center the cap member with respect to the outer cylindrical member 22. It will be noted that the point 16 is thus positioned directly over the center of the oval shaped aperture 52 in the inner cylindrical member so that should the piston be mounted on a connecting rod 'Il having an oil jet 19 in the upper end thereof as is commonly done in some types of engines, particularly Diesel engines, the

jet of oil will pass through the aperture 52 against the point 16 which will deilect the oil outwardly between the upper wall 28 of the outer cylindrical member and the upper wall 48 of the inner cylindrical member Where the oil may absorb heat from the face of the piston and from the humps 50. The oil thus delivered through the aperture 52 may return to the center of the piston by passing through the spaces formed by the ribs 56.

In manufacturing the piston, it is contemplated that the inner cylindrical member 36 and cap member 'I2 will be formed as just described by stamping operations in suitable dies. The outer cylindrical member will also be completely formed with the exception of the upturned ange 35 around its bottom edge.

After shaping the various members as just described, the outer cylindrical member 22, inner cylindrical member 36, a cap 'l2 and ring retaining sleeve 60 will be coated with a mixture of a flux and an alloy of copper or silver or other similar metal that melts at a relatively low temperature. This can be done by painting or spraying the mixture on the several parts. The parts will then be pressed together in their proper relationship and placed in a furnace to raise their temperature above the melting point of the alloy. This causes the alloy to melt and adhere to adjacent surfaces of the several parts so that when they cool, they will be rmly joined together. It is desirable to maintain a non-oxidizing atmosphere in the furnace during the heating operation to assist the flux in preventing the formation of scale and oxides on the several parts.

After the piston has thus been formed, it should be struck in a cylindrical die to set its size and assure that it is round. While it is held in this die, the lower flange 31 may be turned up to keep the lower end of the piston in proper round shape. The ring grooves 62 may then be cut in the usual fashion and, if necessary, the outside surface of the piston may be ground to more accurately determine its size.

Attention is called to the fact that after the tops of the humps 58 have been brazed to the underside of the top wall 28 as described above, the top wall 28 and the upper wall 48 of the inner cylindrical member 36 will, in fact, form the flanges of a series of I-sections of which the humps 50 form the webs. These I-sections provide great strength to the face of the piston Without great weight.

In the modied forms of the invention, reference characters of the same order but in different hundreds are used wherever possible to indicate parts which correspond to similar parts in the preferred form of the invention.

In the modification shown in Figures '1 through 9, the piston |20 consists of a main cylindrical member 22 which is closed at its upper end by an upper cylindrical member |24 of reduced diameter. The two cylinders are joined by the overlapping annular flanges |26 which are formed at the adjacent ends of each cylinder. The flanges |26 form a shoulder on which the piston ring retaining sleeve |60 is positioned. The upper Wall |28 of the upper cylinder |24 is slightly domed and defines a central aperture |30 in the same manner as the upper wall 28 in the preferred form of the invention.

The side walls of the main cylindrical member |22 are pressed inwardly as at |32 at the opposite ends of a diameter of the cylinder and are extruded inwardly as at |34. The inwardly pressed portions |32 will, of course, be formed after the upper cylindrical member |24 has been pressed into place in order to permit the ange |26 on the upper cylindrical member to pass through the lower end of the main cylindrical member.

The inner cylindrical member |36 is the same in all respects as the inner cylindrical member 36 in the preferred form of the invention and so will not be described further. The inner cylindrical member fits tightly Within the upper cylindrical member |24. The extruded portions of the side walls of the main cylindrical member |22 and the inner cylindrical member |36 serve to support the same bearing sleeves |42 and wrist pins |44 as in the preferred form of the invention. The same type of apertures |10 are provided in the inner cylindrical member |36 and upper cylinder |24 to conduct oil away from the oil ring.

The cap member |12 is also the same as the cap member 12 in the preferred form of the invention and functions in the same manner to retain the piston ring retaining sleeve |60 in position. A ange |35 is also formed around the lower end of the piston. The various parts of the modified form of the piston may be securely fastened together by the same brazing process as described in connection with the preferred form of the invention.

In the modified form of the invention shown in Figures l through 12 is shown a main cylindrical member 222 having its upper end closed by an upper cylinder 224 of reduced diameter. The upper end of the main cylinder 222 is provided with an annular inturned shoulder 226, around the inner edge of which a cylindrical flange 221 is turned upwardly. The cylindrical ange 221 is arranged to t tightly within the lower end of the upper cylinder 224, which thus rests upon the shoulder 226.

The upper wall 228 of the upper cylinder 224 is generally flat and has its center pressed downwardly in a point 216 corresponding to the point 16 in the cap member 12 of the preferred form of the invention. The side walls of the main cylindrical member 222 are pressed inwardly as at 232 and extruded as at 234 along the opposite ends of a diameter of the piston.

In place of the inner cylindrical member 36 and |36 of the previous forms of the invention, there are provided a pair of struts 236 which are extruded inwardly as at 240 to support the inner ends of the bearing sleeves 242 within which the Wrist pin 244 is mounted. The upper ends 248 of the struts 236 are flanged inwardly as at 250 and bear against the upper wall 228 of the cylinder 224 to transmit loads between the face of the piston and the wrist pin 244. The sides and bottoms of the struts 236 are flanged inwardly of the piston as at 256 in a continuation of the top flange 250 to strengthen the struts against buckling. The struts are of such a width that the flanges 256 bear against the flange 221 of the main cylindrical member 222 as at 251 approximately midway between the wrist pin and the top of the struts to brace the mid-sections of the struts against buckling.

A piston ring retaining sleeve 260 similar to the retaining sleeve shown in the other forms of the invention is positioned around the side Walls of the upper cylinder 224 and rests upon the shoulder 226 of the main cylindrical member 222. The retaining sleeve 260 is held in place by an annular cap ring 212 which is provided with a cylindrical flange 214 around its outer rim bearing against the top of the piston ring retaining sleeve. Instead of extending completely over the upper Wall 228 of the upper cylinder 224, the retaining ring 212 is welded as at 213 to the outer edge of the upper wall 228. Since the retaining ring 212 does not extend completely over the end of the piston, the point 216 is formed in the upper Wall 228 of the upper cylinder 224 in place of the hole 30 as in the other forms of the invention. The flange 221 and the lower end of the upper cylinder 224 denne a series of apertures 210 communicating with the groove in which the oil ring is positioned.

As in the other forms of the invention, the various parts of the piston 220 may be secured together by the brazing process described and may be easily and inexpensively formed as sheet metal stampings.

While I have describedY my invention in some detail, I intend this description to be an example only and not as a limitation of my invention, to which I make the following claims:

1. A piston comprising a main cylindrical portion, an upper cylindrical portion of reduced diameter, a wall across the top of said upper cylindrical portion, said wall and cylindrical portions being formed of stamped material, inwardly extruded portions formed at each end of a diameter of said main cylindrical portion, bearing sleeves positioned within said inwardly extruded portions, stamped means positioned within said cylindrical portions and extending from said wall to the inner ends 0f said bearing sleeves, a piston ring retaining sleeve positioned around said upper cylindrical portion and against the end of said main cylindrical portion, and means secured to said top Wall for retaining said piston ring retaining sleeve in position.

2. A piston comprising a lower cylindrical portion having an inwardly extending annular shoulder around the upper end thereof, an upper cylindrical portion of reduced diameter extending above said annular shoulder and having an upper wall, a ring retaining sleeve positioned around said upper cylindrical portion and resting on said shoulder, aretaining member secured to said upper wall. and bearing against the upper edge of said sleeve, said cylindrical portions and retaining member being formed as stampings, an inner brace member formed as a stamping and extending from said upper wall downwardly in spaced relationship with said lower cylindrical portion, the side wall of said lower cylindrical portion and said brace member being extruded inwardly of said piston along a diameter of said piston, and a bearing sleeve supported within the extruded portions of said lower cylindrical portion and said brace member.

3. A piston comprising a stamped main cylindrical portion having an annular shoulder around the upper end thereof, a stamped upper cylindrical portion of reduced diameter extending above said shoulder and having an end wall, a rin-g retaining sleeve positioned around said upper cylindrical portion and resting upon said shoulder, a cap member secured to said wall and extending over the end of said retaining sleeve, a brace member secured to said wall and extending downwardly in spaced relationship Within said main cylindrical portion, said ring retaining sleeve and said upper cylindrical portion defining aligned, radial, oil return apertures, said brace member and said main cylindrical portion being extruded along a diameter of said piston, and a bearing sleeve positioned in the extruded portions or said brace member and said main cylindrical portion.

4. A piston comprising an outer cylindrical member having an upper portion of reduced diameter, a first wall formed across the end of said upper portion, a ange turned inwardly around the lower end of said outer member, an inner cylindrical member fitted Within said upper portion and having a top wall spaced from said first wall on said outer cylindrical member, projections formed on said top wall and positioned against said first wall, the lower end of said inner cylindrical member extending downwardly in spaced relationship within the lower portion of said outer cylindrical member, said outer cylindrical member and said inner cylindrical member being extruded inwardly alon-g a diameter of said piston, said outer and inner cylindrical members being formed as stampings, a ring retaining sleeve positioned around said upper portion of said outer cylindrical member, a cap member ser cured to said first wall of said outer cylindrical member and extending over said sleeve, and bearing sleeves positioned within the extruded portions of said cylindrical members.

5. A piston comprising an outer cylindrical member having an integral upper portion of reduced diameter with a top wall defining an aperture in the center thereof, an inner cylindrical 'member positioned within said upper portion of said outer member and having a second wall spaced from said top wall, projections pressed upwardly from said second wall into contact with said top wall, the center of said second wall defining an upwardly flanged aperture underneath said aperture in said top wall, inwardly extruded portions formed in said outer and inner cylindrical members along a diameter of said piston, vertical ribs pressed inwardly in said inner cylindrical member and extending upwardly from said extruded portions, a cap member positioned on top of said top wall and having a downwardly pressed point extending through the aperture in said top wall, means securing together said inner and outer cylindrical members and said cap, a ring retaining sleeve positioned around said upper portion of said outer cylindrical member and below said cap member, and bearing sleeves positioned in said inwardly extruded portions of said outer and inner members.

6. A piston comprising a cylindrical stamping Cil having a lower portion of large diameter and an upper portion of relatively reduced diameter with a top wall extending across the end thereof, the side walls of said large diameter cylindrical portion being extruded inwardly of said piston and defining aligned apertures along a diameter of said piston, and cylindrical flanges formed around said apertures.

7. A reinforcing member for a stamped piston comprising a cylindrical stamping having an upper wall defining an oval shaped central aperture, an upwardly extending flange formed around said aperture, upwardly extending projections formed in said upper wall, the side walls of said stamping being pressed inwardly and defining co-axial apertures, vertical ribs pressed in i. the side walls of said stamping and extending between said inwardly pressed portions and said top wall, and cylindrical flanges formed around said apertures.

8. A reinforcing member for a stamped piston comprising a cylindrical stamping having an upper wall, upwardly extending projections formed on said upper wall, inwardly pressed, vertically extending ribs formed in the side walls of said stamping, other inwardly pressed portions in the side walls of said stamping and defining coaxial apertures along a diameter of said stamping, the side Walls of said stamping being cut away between said other inwardly pressed portions.

9. A reinforcing member for a stamped piston comprising a cylindrical stamping having an upper wall, upwardly extending projections formed on said upper wall, inwardly pressed, vertically extending ribs formed in the side walls of said stamping, other inwardly pressed portions in the side walls of said stamping and dening co-axial apertures along a diameter of said stamping.

10. A piston comprising a pair of stamped cylindrical members positioned in telescopic relationship and having radially spaced lower ends defining a series of aligned apertures along a diameter of the piston, the upper ends of said stampings being secured together, and a piston ring retaining sleeve positioned around one end of one of said members.

l1. A piston comprising a cylindrical stamping having a shoulder formed therearound, a sleeve having piston ring grooves cut therein positioned around said stamping and against said shoulder, and a cap member secured to said stamping and bearing against the opposite end of said sleeve from said shoulder.

12. A piston comprising an outer cylindrical member having an inwardly turned ange along the top thereof, an upper cylindrical member of reduced diameter having an outwardly turned flange along the lower edge thereof, a top wall formed on said upper cylindrical member, said flanges on said cylindrical members being secured together in overlapping relationship, a sleeve having ring retaining grooves formed therein pe sitioned around said upper cylindrical member, and a cap member secured to said top wall and overlying the upper end of said sleeve.

13. A piston comprising an upper cylindrical member formed as a stamping and having a top wall, a ange turned outwardly around the bottom of said upper member, an inner cylindrical member pressed within said upper cylindrical member and having a lower portion extending therebelow, an outer cylindrical member of greater diameter than said inner cylindrical member, an inwardly turned iiange formed on the upper end of said outer member and overlapping said outwardly turned flange on said upper member, and means formed on the side walls of said inner and outer cylindrical members for supporting a wrist pin.

14. A piston comprising an upper cylindrical member having a'top Wall enclosing the end thereof, a lower cylindrical member having a shoulder turned inwardly along the upper end thereof, a cylindrical flange turned upwardly from the inner edge of said shoulder and positioned telescopically within the lower end of said upper cylindrical member, a sleeve having ring retaining grooves formed therein positioned around said upper cylindrical member and resting on said shoulder, parallel struts extending from said top wall to within said lower cylindrical member and deining co-axial apertures along a diameter of said piston, the side walls of said lower cylindrical member defining flanged apertures co-axial with said apertures vin said struts, bearing retaining sleeves positioned in A said apertures, and a cap ring secured around the edge of said top wall and bearing against the upper end of said sleeve.

15. A piston comprising an upper cylindrical member having a closed upper end, a lower cylindrical member having an inwardly extending shoulder formed around the upper end thereof, a cylindrical flange formed along the inner edge of said shoulder and positioned in telescopic relationship with the lower edge of said upper cylindrical member, struts having flanges formed around the edges thereof and extending from the closed upper end of said upper cylindrical member downwardly to within said lower cylindrical member, the lower ends of said struts defining co-axial apertures, the side walls of said lower member defining other apertures co-axial with said first apertures, a piston ring retaining sleeve positioned around said upper member, and means for supporting a wrist pin supported in said aperture.

16. A piston comprising an upper cylindrical member having a. closed upper end, a lower cylindrical member having an inwardly extending shoulder formed around the upper end thereof, a cylindrical ange formed around the inner edge of said shoulder and positioned in telescopic relationship with the lower edge of said upper member, a stamped reinforcing member extending from said closed upper end to within said lower member, the lower ends of said reinforcing member and said lower cylindrical member dening spaced, aligned apertures along a diameter of said piston, and a ring retaining cylinder positioned around said upper cylindrical member.

17. A piston comprising an upper cylindrical member having a top wall enclosing the end thereof, a lower cylindrical member having a shoulder turned inwardly along the upper end thereof, a cylindrical flange turned upwardly from the inner edge of said shoulder and positioned telescopically within the lower end of said upper cylindrical member, a sleeve having ring retaining grooves formed therein positioned around said upper cylindrical member and resting on said shoulder, parallel struts extending from said top wall to within said lower cylindrical member and dening co-axial apertures along a diameter of said piston, the side walls of said lower cylindrical member dening iianged.

apertures co-axial with said apertures in said struts, a cap ring secured around the edge of said top Wall and bearing against the upper end of said sleeve, said parts of said piston being integrally united.

18. A composite piston comprising a body stamping having a cylindrical skirt, a piston ring sleeve telescoping said body stamping, an inner reinforcing stamping received within and spaced from said body stamping over the major portion of its top area, and contacting one another at adjacent areas, means rigidly engaging said body stamping and reinforcing stamping respectively, and maintaining said stampings in partially spaced relation, and means integrally joining said stampings and said spacing means and stampings.

HARRY F. WOOD.

DISCLAIMER 2,341,836.Harry F. Wood, Kenosha, Wis. PIsToN. Patent dated Feb. 15, 1944. Disclaimer filed Sept. 12, 1946, by the inventor; the assignee, Nash-Keloinator Corporation, acquiescing.

Hereby enters this disclaimer to claim 6 in said specification.

[Oficial Gazette October 8, 1946.] 

